Is there a question associated with this statement?
OWA is a function of Microsoft Exchange and not Microsoft Outlook/Microsoft
Office. For an expert answer, you should post this (as a question) to the
Exchange community:
In addition to K. Orland's reply, my guess is that either the mail admin is
very much behind with updating or you still have the old MIME client
installed.
See http://www.msoutlook.info/question/15
